Pneumatic positioning apparatus and parts therefor or the like

ABSTRACT

A plurality of separate pneumatically operated actuators disposed in aligned and abutting relation to provide a linear positioning unit having opposed ends with each actuator being individually operable to linearly extend itself when actuated and thereafter to linearly collapse itself when deactuated whereby one end of the unit will be correspondingly linearly extended relative to the other end thereof and thereafter be linearly collapsed relative to the other end thereof. A control device being operatively interconnected to the one end of the positioning unit to be controlled in relation to the position of the one end relative to the other end thereof and control means for directing a source of pneumatic fluid to at least one of the actuators to extend the one end of the unit by the degree of actuation of the one actuator and for thereafter disconnecting the source from that one actuator to collapse the one end of the unit by the degree of deactuation of the one actuator.

Waite States Patent 1 Puster [54] PNEUMATIC POSITIONING APPARATUS ANDPARTS THEREFOR OR THE LIKE [75] Inventor: Louis M. Puster, Knoxville,Tenn.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Oct; 22, 1971 [21] Appl. No.: 191,614

Related US. Application Data [62] Division of Scr. No. 865,079, Oct. 9,1969, Pat, No.

52 U.S. c1. 92/13, 92/13.3, 92/151,

92/163, 92/165 [51] Int. Cl. ..F15b 15/24, F16j 11/02 [58] Field ofSearch 92/128, 151, 150,

[56] References Cited UNITED STATES PATENTS 234,407 11/1880 Jay 92/128 X2,480,633 8/1949 Christensen 92/164 X 2,969,042 1/1961 Litz et al 91/1673,138,073 6/1964 Whitehouse 92/165 X 3,608,438 9/1971 Thomas et al.92/165 Primary Exam-inen-Irwin C. Cohen Attorney Auzville Jackson, Jr.and James T. Candor [57] ABSTRACT A plurality of separate pneumaticallyoperated actuators disposed in aligned and abutting relation to providea linear positioning unit having opposed ends with each actuator beingindividually operable to linearly extend itself when actuated andthereafter to linearly collapse itself when deactuated whereby one endof the unit will be correspondingly linearly extended relative to theother end thereof and thereafter be linearly collapsed relative to theother end thereof. A control device being operatively interconnected tothe one end of the positioning unit to be controlled in relation to theposition of the one end relative to the other end thereof and controlmeans for directing a source of pneumatic fluid to at least one of theactuators to extend the one end of the unit by the degree of actuationof the one actuator and for thereafter disconnecting the source fromthat one actuator to collapse the one end of the unit by the degree ofdeactuation of the one actuator.

7 Claims, 8 Drawing Figures Patented June 19, 1973 3,739,693

4 Sheets-Shoot 1 Patented June 19, 1973 3,739,693

4 Sheets-Sheet a FIGS Patented June 19, 1973 4 Sheets-Sheet 4.

PNEUMATIC POSITIONING APPARATUS AND PARTS THEREFOR OR THE LIKE Thisapplication is a divisional patent application of its copending parentpatent application, Ser. No. 865,079, filed Oct. 9, 1969 now Pat. No.3,633,465, and is assigned to the same assignee to whom the parentapplication is assigned.

This invention relates to an improved pneumatically operated apparatusfor positioning a controlled device or the like in desired positionsthereof, this invention also relating to improved parts for such apositioning apparatus or the like.

It is well known that various pneumatically operated positioning deviceshave been provided wherein a controlled device has its operatingcondition changed in proportion to the degree of actuation of one ormore pneumatically operated actuators forming part of the positioningapparatus.

It is a feature of this invention to provide an improved pneumaticallyoperated positioning apparatus of the above type.

In particular, one embodiment of this invention provides a tubularhousing member having a plurality of separate pneumatically operatedactuators disposed in aligned and abutting relation in a tubular housingto provide a linear positioning unit having opposed ends, each actuatorbeing individually operable to readily extend itself when actuated andthereafter to linearly collapse itself when deactuated whereby one endof the unit will be correspondingly linearly extended relative to theother end thereof and thereafter be linearly collapsed relative to theother end thereof. A control device is operatively interconnected to theone end of the positioning unit to be controlled in relation to theposition of the one end of the unit relative to the other end thereof. Asource of pneumatic fluid is directed to a control means which comprisesindividual solenoid operated valves for each of the pneumaticallyoperated actuators whereby when one of the solenoid operated valvesdirects the pneumatic source to its respective actuator to extend theone end of the unit by the degree of actuation of that one actuator, thecontrol device is proportionally adjusted.

Therefore, it is an object of this invention to provide an improvedpneumatically operated positioning apparatus having one or more of thenovel features set forth above or hereinafter shown or described.

Another object of this inventionis to provide an improved pneumaticallyoperated actuator for such an apparatus or the like, the actuator havingone or more of the novel features set forth above or hereinafter shownor described.

Other objects, uses and advantages of this invention are'apparent from areading of this description which proceeds with'reference to theaccompanying drawings forming a part thereof and wherein:

FIG. 1 is a side view, partially in cross section, illustrating theimproved pneumatically operated positioning apparatus and control systemof this invention.

FIG. 2 is a cross-sectional view taken substantially on line 2-2 of FIG.1.

FIG. 3 is an enlarged, fragmentary, cross-sectional view of a portion ofthe positioning apparatus of FIG. 1 illustrating certain of thepneumatically operated actuators thereof in actuated condition.

FIG. 4is a top perspective view of one of the improved pneumaticallyoperated actuators of the apparatus of FIG. 1.

FIG. 5 is an exploded perspective view of the parts forming thepneumatic actuator of FIG. 4.

FIG. 6 is a cross-sectional view of the pneumatically operated actuatorof FIG. 4 and is taken substantially on line 66 of FIG. 4.

FIG. 7 is a top view of one of the solenoid operated valve means for theapparatus of FIG. 1.

FIG. 8 is a partial cross-sectional view of the solenoid operated valveof FIG. 7 and is taken on line 8-8 thereof.

While the various features of this invention are hereinafter describedand illustrated as being particularly adapted to control a set pointindicator and its controllingdevice, such as for a textile controlsystem or the like, it is to be understood that the various features ofthis invention can be utilized singly or in any combination thereof toprovide positioning means for other devices as desired, such as forpositioning a valve, pressure regulator or other similar devices,individually or collectively.

Therefore, this invention is not to be limited to only the embodimentillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIGS. 1 and 2, the improved pneumatically operatedpositioning apparatus and control system of this invention is generallyindicated by the reference numeral 10 and comprises a frame means 11carrying a device 12 that is adapted to have its output varied inrelation to the position of an actuator rod 13 relative to the frame 11,the actuator rod 13 being suitably coupled to an indicating pointer 14which indicates to the viewer the position of the actuator rod 13 and,thus, the set output function of the control device 12.

A cylindrical housing means 15 is secured to the frame means 11 in anysuitable manner, such as by brackets 16 respectively at the opposed ends17 and 18 of the cylinder 15. The opposed ends 17 and 18 of the cylinder15 are respectively closed by end closure caps 19 and 20 held thereon inplug fashion by threaded retuators 23 are disposed in aligned abuttingrelation to provide a linear positioning unit, generally indicated bythe reference numeral 24, in the cylinder 15 with the positioning unit24 having opposed ends 25 and 26.

A dash-pot means, generally indicated by the reference numeral 27 inFIG. 1, is also disposed in the cylinder or housing means 15 andcomprises a piston 28 and cooperating cylinder 29 with the cylinder 29being movable in the housing 15 and having its lower'end 30 abuttingagainst the upper end 25 of the positioning unit 24. The piston 28 isheld stationary relative to the cylinder 29 and has a stem 31 projectingout of the upper end 32 of the cylinder 29 and is threadedlyinterconnected to the upper end cap 19 of the housing means whereby theposition of the piston 28 can be adjusted relative to the housing means15, if desired.

The cylinder 29 of the dash-pot means 27 is filled with a suitabledampening fluid, such as silicone, so as to provide means for cushioninglinear movement of the positioning unit 24 in the housing means 15 tothe actuator rod 13 of the control device 12 as will be apparenthereinafter, the dash-pot means 27 operatively interconnecting thepositioning unit 24 to the actuating rod 13 of the control device 12 bysuitable linkage means 33.

In particular, the upper end 32 of the cylinder 29 of the dash-pot means27 has an arm 34 fastened therethrough and projecting out through a slot35 in the housing means 15 so as to be disposed in engagement with a pin36 transversely carried by a pivotally mounted lever 37 which isinterconnected through linkage means 38, 39 and 40 to the actuator rod13 and set point indicator 14 so that upward and downward movement ofthe arm 34 of the dash-pot means 27 will cause correspondingly downwardand upward movement of the actuating rod 13 as will be apparenthereinafter. In order to maintain the pin 36 of the lever 37 inengagement against the arm 34 of the dash-pot means 27, a suitabletension spring 41 is provided and has one end 42 interconnected to thelink 38 and the other end 43 thereof interconnected to the upper bracket16.

Since the actuators 23 of the positioning unit 24 are separate from eachother, as well as from the dash-pot means 27 in the housing means 15,another tension spring 44 is provided and has one end 45 interconnectedto the arm 34 and the other end 46 thereof interconnected to the lowerbracket 16 whereby the force of the tension spring 44 normally tends tomaintain all of the actuators 23 in their collapsed and deactuatedcondition and with the cylinder 29 of the dashpot means 27 in engagementwith the upper end 25 of the positioning unit 24.

Each actuator 23 of the positioning unit 24 is adapted to beindividually operable to linearly extend itself when actuated andthereafter to linearly collapse itself when deactuated whereby the upperend 25 of the positioning unit 24 will be correspondingly linearlyextended in an upward direction and thereafter be linearly collapsed ina downward direction depending upon the degree of actuation of theparticular actuator 23 and the degree of deactuation thereof. Since suchupward and downward movement of the upper end 25 of the positioning unit24 operates to correspondingly move the cylinder 29 of the dash-potmeans 27, the dampening fluid in the cylinder 29 serves to dampen suchmovement of the upper end 25 of the positioning unit 24 to the actuatingrod 13 of the control device 12 so that the control device 12 is slowlychanged and thereby does not have sudden overshoots or undershoots, thepin 36 sliding on the arm 34 of the cylinder 29 of the dash-pot means 27so as to permit clockwise or counterclockwise movement of the lever 37depending upon upward or downward movement of the end 25 of thepositioning unit 24.

A plurality of electrically operated valve means 47 are respectivelysecured to the frame means 11 with one valve means 47 being providedfor-each pneumatically operated actuator 23 which, in the embodimentillustrated in FIG. 1, comprises nine valve means 47 and ninepneumatically operated actuators 23. Each valve means 47 is operativelyinterconnected to a pneumatic source 48 in a manner hereinafterdescribed and is adapted, when actuated, to direct the pneumatic source48 to its respective actuator 23 by an outlet conduit means 49 so as tolinearly extend or actuate that actuator 23. Thereafter, that particularvalve means 47 can disconnect the pneumatic source 48 from itsrespective actuator 23 while interconnecting the atmosphere thereto soas to deactuate its particular actuator 23 whereby the same willlinearly collapse under the force of the tension spring 44.

Each valve means 47, when deenergized, prevents communication betweenthe pneumatic source 48 and its respective actuator 23 whileinterconnecting its respective actuator 23 to the atmosphere. However,when the respective valve means 47 is energized, the same disconnectsthe atmosphere from its respective actuator 23 and interconnects thepneumatic source 48 thereto.

Each valve means 47 has a pair of terminals 50 and 51 with the terminals50 of the valve means 47 being respectively interconnected to anelectrical lead 52 that is interconnected to a power source line L Theother terminal 51 of each valve means 47 is interconnected to respectiveleads 53 which are adapted to be selectively, collectively or in anycombination thereof, interconnected to the other power source lead L, bya suitable control means 54, such as a computer, tape or card reader,etc., so as to control the operation of the control device 12 in amanner hereinafter set forth.

Each pneumatically operated actuator 23 can be formed in a like mannerand the details of one such pneumatically operated actuator 23 will nowbe described and reference is made to FIGS. 4, 5 and 6.

As illustrated in FIGS. 4, 5 and 6, the actuator 23 comprises twocup-shaped housing members 55 and 56 formed in cylindrical form andrespectively having open ends 57 and 58, the open end 58 of thecupshaped housing member 56 being inwardly offset and being externallythreaded at 59 so as to be threaded to the internal threaded portion 60of the other cupshaped housing member 55 whereby the thus interconnectedcup-shaped housing members 55 and 56 define a cylinder means 61 having atransverse cross-sectional configuration closely resembling thetransverse crosssectional configuration of the inside of the cylinder orhousing means 15 so as to be disposed in closed relation to the internalperipheral surface of the housing means 15 while permitting movementtherebetween for the aforementioned linear expansion and contraction ofthe positioning unit 24. A piston member 62 has an enlarged cylindricalportion 63 disposed in the open end 58 of the cup-shaped member 56 andhas an annular groove 64 receiving an annular O-ring 65 for sealingagainst the internal peripheral surface 66 of the housing member 56while permitting axial movement of the piston member 62 relativethereto. The piston member 62 has its lower surface 166 interrupted by acavity 67 to cooperate with the housing member 56 to define a chamber 68therebetween.

In addition, the lower surface 166 of the piston member 62 is beveled at69 at the corner thereof so as to be in fluid communication with atransverse passage means 70 formed radially through the cup-shapedhousing member 56 and being interconnected to a tubular insert 71 thatis adapted to be interconnected to the respective conduit means 49 of arespective valve means 47 for permitting the pneumatic source 48 to bedirected to the cavity 68 of the actuator 23 or for-interconnecting theatmosphere thereto.

The piston member 62 includes a reduced portion 72 cooperating with thelarge portion 63 to define an annular shoulder 73 for abutting againstthe inside surface 74 of the closed end 75 of the upper cup-shapedhousing member 55 so as to limit upward movement of the piston member 62when the actuator 23 is interconnected to the pneumatic source, thereduced portion 72 of the piston member 62 projecting out through asuitable opening 76 in the closed end 75 of the cupshaped housing member55 so as to have its flat end 77 for engaging against the cylinder means61 of the actuator 23 above the same in the positioning unit 24.

By providing the threaded relation 59 and 60 between the cup-shapedhousing members 55 and 56, the stroke or linear distance that the pistonmember 62 can travel in an upward direction in FIG. 6 when having itscavity 68 interconnected to the pneumatic source 48 can be readilyadjusted and once adjusted to the desired position, suitable set screws78 can be tightened to hold the cup-shaped housing members 55 and 56 inthe desired adjusted threaded relation therebetween.

Therefore, it can be seen that each actuator 23 can have a differentstroke setting than the other actuators 23 as determined by theparticular threaded relation between the two cup-shaped housing members55 and 56 thereof which define the cylinder means 61 thereof. Therefore,with pressure applied to the tubing 71 of a particular actuator 23, thepiston member 62 moves up until the shoulder 73 thereof strikes againstthe end 75 of the housing member 55 and when the cavity 68 thereof isinterconnected to the atmosphere and a load is applied to the pistonmember 62 thereof, such as by the tension spring 44 of FIG. 1, thepiston 62 is driven downwardly until the same bottoms against the closedend 79 of the lower cup-shaped housing member 56.

Thus, it can be seen that each pneumatically operated actuator 23 ofthis invention can be formed of relatively simple and inexpensive partsto be assembled together in a simple and effective manner to permitseparate adjustment of the stroke thereof and can be disposed in thehousing means to provide the positioning unit 24, the housing means 15having another slot 80 in the side thereof and out through which thetubing 71 of the actuators 23 can project to not only permit axialmovement of the actuators 23 in the housing means 15, but also to guidethe same in the housing means 15 and prevent rotational movementtherein.

The valve means 47 for the apparatus 10 of this invention are identicaland one such valve means 47 is illustrated in FIGS. 7 and 8 and will nowbe described.

As illustrated in FIGS. 7 and 8, each valve means 47 comprises atwo-piece bracket 81 with the lower part 82 thereof carrying a housingmeans 83 supporting a solenoid coil 84 having its opposed endsrespectively interconnected to the terminals 50 and 51, the coil 84having core means 85 for attracting an armature or clapper 86 pivotallymounted to the bracket means 81 in any suitable manner at a point 87intermediate its opposed ends 88 and 89. The armature or clapper 86 isnormally urged to the position illustrated in FIG. 8 by a tension spring90 having one end 91 interconnected to the end 89 of the armature 86 andthe other end 92 interconnected to the bracket means 81. An opening 93passes through the armature 86 and is covered at its lower end by a leafspring 94 attached to the armature 86 by a pair of eyelets 95 passingthrough suitable openings in the leaf spring 94 which are oversized sothat the leaf spring 94 can bow relative to the armature 86 as will beapparent hereinafter.

Another housing member 96 is carried by an upper arm 97 of the bracketmeans 81 and has a cavity 98 formed therein and receiving a valve seatmember 99 that cooperates with an O-ring 100 to seal the cavity 98 abovean outwardly directed annular flange 101 of the valve seat member 99from the exterior of the housing 96. A stepped bore 102 passes throughthe valve seat member 99 whereby the lower end 103 of the bore 102 isexposed to the atmosphere and the upper end 104 of the bore 102 is inaligned relation with a passage 105 formed in the housing 96 andinterconnected to a cross passage 106 formed in the housing 96 and beingrespectively interconnected at opposed ends to tubular nipple fittings107 and 108, as illustrated in FIG. 7.

The upper end 104 of the stepped bore 102 of the valve seat member 99 isalso in communication with a transverse recess 109 that communicateswith the cavity 98.

The juncture 110 that the passage 105 makes with the cavity 98 in thehousing member 96 defines a valve seat adapted to be opened and closedby a ball valve member 111. Similarly, the stepped bore 102 in the valveseat member 99 defines a valve seat 112 adapted to be opened and closedby the ball valve 111.

An actuating rod 113 projects loosely into the end 103 of the steppedbore 102 so as to have its upper end 1 14 engageable with the ball valvemember 111 and its lower end 115 engageable against the leaf spring 94of the clapper or armature 86.

Thus, when the coil 84 of the particular valve means 47 is deenergized,the tension spring 90 maintains the armature 86 in the positionillustrated in FIG. 8 whereby the armature 86, through the push rod 113,maintains the ball valve member 111 away from the valve seat 112 andinto sealing engagement with the valve seat 110 so that the cavity 98 isdirectly interconnected to the atmosphere through the cross recess 109and open valve seat 112. However, when the coil 84 of the particularvalve means 47 is energized by being interconnected to the power sourceleads L, and L by the control device 54, the end 88 of the armature 86is pulled downwardly in FIG. 8 so that the push rod 113 follows suchmovement and permits the ball valve member 11 1 to move away from thevalve seat 110 and into sealing engagement with the valve seat 112whereby the cavity 98 is sealed from the atmosphere and is in fluidcommunication with the cross passage 106 in the housing means 96.

The cavity 98 of the housing means 96 is always in communication with apassage means 116 which receivesfa tubular extension nipple 117 that isadapted to be interconnected to the conduit means 49 that leads v to therespective actuator 23 for that valve means 47.

As illustrated in FIG. 1, all of the cross passages 106 of the ninevalve means 47 are adapted to be interconnected to the pneumatic source48 by having the nipple extension 107 on the lower valve means 47 ofFIG. 1 fluidly interconnected to the pneumatic source 48 by a couplingconduit means 118 and its other nipple extension 108 interconnected tothe nipple means 107 of the next adjacent valve means 47 by a couplingconduit means 119. Thus, all of the valve means 47 have the nippleextensions 107 and 108 thereof coupled in series with the uppermostvalve means 47 in FIG. 1 having its nipple extension 108 sealed from theatmosphere.

Therefore, in the control system 10 of this invention, when a particularsolenoid coil 84 of a particular valve means 47 is energized, the end 88of the armature clapper 86 thereof is pulled downwardly against the coremeans 85 and the stem or rod 113 follows such movement and is ofsufficient length to permit the ball valve member 111 to seat againstthe vent valve seat 112 so as to permit pressurized fluid which issupplied through the tubing adaptors 107 or 108 to flow through thepassage 106 and opened valve seat 110 to the outlet passage l16 and,thus, to its respective actuator means 23. When that particular solenoidcoil 84 is subsequently deenergized, the tension spring 90 snaps theleft-hand end 88 of the clapper 86 upwardly so that the stem or rod 113engages the ball valve member 1 l 1 and unseats it from the vent valveseat 112 and forces it against the supply valve seat 110 to close offthe supply of air pressure from passage 105 and venting the pressurizedair from its interconnected actuator 23 through the open vent valve seat112 to the atmosphere, such upward snapping movement of the armature 86permitting the leaf spring 94 to bow and absorb the shock of the valvemember 86 striking the stem or rod 113 and its seating action of theball 111 against the supply valve seat 110.

The operation of the apparatus and control system 10 of this inventionwill now be described.

With all of the actuators 23 in their deactuated condition, thepositioning unit 24 is in the position illustrated in FIG. 1 whereby theactuating rod 13 of the control device 12 is at one setting thereof.However, should it be desired or determined that the output of thecontrol device 12 should be increased or decreased as the case may be,the control means 54 interconnects the power source leads L to theparticular lead 53 of the particular valve means 47 or to several leads53 of particular valve means 47 as the case may be so that one or moreof the valve means 47 will have the coils 84 thereof energized.

Pressurized fluid is then adapted to flow from the source 48 to therespective actuators 23 of the energized valve or valves 47interconnected therewith.

' Thus, the pistons 62 of the actuators 23 extend in the mannerillustrated in FIG. 3 moving the end 25 of the stack 24 upwardly theamount of the actuated piston strokes. The dash-pot cylinder 29 and arm34 also move up, rotating the lever 37 through the pin 36 in a clockwisedirection with the pin 36 sliding on the arm 34. Such clockwise movementof the lever 37 through the linkage 38, 39, 40 moves the indicator 14 ina clockwise direction and the actuating rod 13 in a downward directionso as to change the setting of the control device 12 proportionally tothe amount of up movement of the end 25 of the positioning unit 24, thedashpot means 27 serving as a dampening device so that the set point ofthe control device 12 is slowly changed eliminating sudden overshootsand jumping of the control device 12.

If the solenoid valves 47 previously energized are now deenergized,pressurized air is vented from the actuated actuators 23 through theirrespective deener-.

gized solenoid valves 47 permitting the tension spring 44 to return theextended pistons 62 to their originally collapsed conditions so that thecylinder 29 of the dashpot means 27 moves downwardly permitting thelever 37 to rotate in a counterclockwise direction under the force ofthe tension spring 41 and move the set point indicator 14 back to itsoriginal position and moving the actuator rod 13 back to its originalposition so that the control device 12 is set back to its originalvalue.

The rate of action of the positioning unit 24 for changing the settingof the control device 12 is determined by the dash-pot means 27. Thisrate of movement in the dash-pot means 27 is determined by the viscocityof the fluid in the cylinder 29 and the clearance between the outsidediameter of the piston 28 and the inside diameter of the cylinder 29since the piston 28 is held stationary and the cylinder 29 is moved byspring 44 forcing fluid in the cylinder means 29 past the stationarypiston 28.

From the above description, it can be seen that the amount of set pointchange of the control device 12 is directly proportional to the amountof stroke that the actuators 23 will make when actuated. Therefore, withthe nine actuators 23 illustrated, nine different amounts of set pointchange can be fed into the control device 12. By energizing the solenoidvalves in combination and choosing proper strokes for the differentactuators 23, almost any set point change to the control device 12 canbe achieved. The solenoid valves 47 can be energized by many differentdevices, such as a computer, tape or card reader, etc.

For example, to fit a computer to the apparatus 10 of this invention,the following description will be based on binary numbering Logicalthough it is to be understood that other Logic systems could be usedsuch as decimal, binary decimal, etc.

However, with a binary numbering logic system, the strokes of the nineactuators 23 will be functions of the following binary numbering system:1, 2, 4, 8, 16, 32, 64, 128 and 256 which totals to 511. Assuming eachnumber represents 1 F., the system 10 can obtain a 0 F. to 511 F. rangechange in l F. steps by choosing the right combination of actuators 23.For example, 200 F. is achieved by actuating the 128 F., 64 F. and the 8F. actuators 23 while 199F. is achieved by actuating the 128 F., 64 F.,4F., 2 F. and 1 F. actuators 23. Actually, each actuator 23 will make astroke which is some multiple of the above number to obtain more totaltravel. in this instance, the actuators 23 can be chosen for stroketravel of 0.0025 of an inch per 1 F. Therefore, the 1 F. actuator 23makes 0.0025 inch travel; the 2 F actuator 23 makes 0.005 inch travel;the 4 F. actuator 23 makes 0.010 inch travel; the 8 F. actuator 23 makes0.020 inch travel; the 16 F. actuator 23 makes 0.040 inch travel; the 32F. actuator 23 makes 0.080 inch travel; the 64 F. actuator 23 makes0.160 inch travel; the 128 F. actuator 23 makes 0.320 inch travel; andthe 256 F. actuator 23 makes 0.640 inch travel. 1

Therefore, for a total of 51 1 F. span controller, the stack 24 ofactuators 23 would have a total travel of 1.2775 inches in 0.0025 inchsteps.

Having available a total of 511 F. span controller, each span less thanthat could be used; for instance, 200 F. say from 50 F. to 250 F. with32 F., 16 F. and 2 F. actuators 23 actuated, the set point indicator 14would be calibrated to read 50 F. To prevent damaging over travel, stem31 can be adjusted to bottom out on the inside of the housing orcylinder 29 and serve as a stop for the apparatus 10.

Therefore, it can be seen that not only does this invention provide animproved pneumatically operated positioning apparatus, but also thisinvention provides an improved pneumatically operated actuator for suchan apparatus or the like.

What is claimed is:

1. A pneumatically operated actuator comprising a pair of cup-shapedhousing members respectively having their open ends provided withthreaded portions that are adjustable secured together in threadedtelescoping relation to define a cavity between their respective closedends, and a piston member slidably disposed in the open end of one ofsaid housing members to define a chamber between said piston member andsaid closed end of said one housing member, the other housing memberhaving an opening through its said closed end in communication with saidcavity, said piston member having an extension projecting through saidopening whereby the stroke of said actuator is determined by said pistonmember abutting against the respective closed ends of said housingmembers, said threaded portion of said one housing member being inwardlyoffset from said closed end thereof, holding means being carried by saidone housing member to secure said housing members together in thedesired adjusted telescoping relation thereof, said holding meanscomprising a set screw threaded in a threaded through bore in said onehousing member and having a portion thereof extending beyond said endwall of said one housing member outboard of said inside side surfacethereof and abut against the open end of said other housing member, saidset screw being adapted to be adjusted to permit said free end of saidother housing member to be adjusted to abut against said one housingmember adjacent said offset threaded portion thereof.

2. A pneumatically operated actuator as set forth in claim 1 whereinsaid holding means comprises another set screw that is threaded inanother threaded through bore in said one housing member and has aportion thereof extending beyond said end wall of said one housingmember outboard of said inside surface thereof and abut against saidopen end of said other housing member.

3. A pneumatically operated actuator as set forth in claim 2 whereinsaid set screws are disposed on opposite sides of said chamber.

4. A pneumatically operated actuator as set forth in claim 1 whereineach housing member has a substantially circular transversecross-sectional configuration.

5. A pneumatically operated actuator as set forth in claim 1 whereinsaid piston member has an end surface for abutting against said closedend of said one housing member, said end surface having a recess formedtherein.

6. A pneumatically operated actuator as set forth in claim 5 whereinsaid end surface of said piston member is beveled at the edge thereof.

7. A pneumatically operated actuator as set forth in claim 1 whereinsaid piston member carries an O-ring to seal against said one housingmember while providing movement therebetween.

1. A pneumatically operated actuator comprising a pair of cupshapedhousing members respectively having their open ends provided withthreaded portions that are adjustable secured together in threadedtelescoping relation to define a cavity between their respective closedends, and a piston member slidably disposed in the open end of one ofsaid housing members to define a chamber between said piston member andsaid closed end of said one housing member, the other housing memberhaving an opening through its said closed end in communication with saidcavity, said piston member having an extension projecting through saidopening whereby the stroke of said actuator is determined by said pistonmember abutting against the respective closed ends of said housingmembers, said threaded portion of said one housing member being inwardlyoffset from said closed end thereof, holding means being carried by saidone housing member to secure said housing members together in thedesired adjusted telescoping relation thereof, said holding meanscomprising a set screw threaded in a threaded through bore in said onehousing member and having a portion thereof extending beyond said endwall of said one housing member outboard of said inside side surfacethereof and abut against the open end of said other housing member, saidset screw being adapted to be adjusted to permit said free end of saidother housing member to be adjusted to abut against said one housingmember adjacent said offset threaded portion thereof.
 2. A pneumaticallyoperated actuator as set forth in claim 1 wherein said holding meanscomprises another set screw that is threaded in another threaded throughbore in said one housing member and has a portion thereof extendingbeyond said end wall of said one housing member outboard of said insidesurface thereof and abut against said open end of said other housingmember.
 3. A pneumatically operated actuator as set forth in claim 2wherein said set screws are disposed on opposite sides of said chamber.4. A pneumatically operated actuator As set forth in claim 1 whereineach housing member has a substantially circular transversecross-sectional configuration.
 5. A pneumatically operated actuator asset forth in claim 1 wherein said piston member has an end surface forabutting against said closed end of said one housing member, said endsurface having a recess formed therein.
 6. A pneumatically operatedactuator as set forth in claim 5 wherein said end surface of said pistonmember is beveled at the edge thereof.
 7. A pneumatically operatedactuator as set forth in claim 1 wherein said piston member carries anO-ring to seal against said one housing member while providing movementtherebetween.